Pulping and shredding system



1932- GS. WlTHAM. JR

PULPING AND SHREDDING SYSTEM 4 Sheets-Sheet Filed Sept. 1, 1927 W- 8,1932. G. s. WlTHAM. JR 1,887,225

PULPING AND SHREDDING SYSTEM Filed Sept. 1, 1927 4 Sheets-Sheet 2 lNl/ENTOR fiearge @d/J//d 1447/70/77, J:

,ATTORNEY PULPING AND SHREDDING SYSTEM Jylllllll/lzgbv/ ATTQRNEY Nov. 8,1932.

G. s. WITHAM JR PULPING AND SHREDDING SYSTEM Filed Sept. 1, 1927 4Sheets-Sheet 4 OOOOOOOO OOOOOOO qco aoooo fir v I AT ORNEY Patented Nov.8, 1932 UNITED STATES PATENT OFFICE GEORGE STANFORD WITHAM, JR, OFHU'IDSON FALLS,NEW YORK PULPI NG AND SHREDDING SYSTEM I Applicationfiled September My invention relates to paper making, and

particularly to the preparation of stock for delivery to the papermachine. It concerns both the method of procedure or process, theapparatus, and-the arrangement of the apparatus whereby partiallyprepared fibrous materials are reduced or converted to' the proper stateor condition for use in a paper making machine, and whereby the processof reduction or conversion is carried on continuously.

In the preparation of stock for delivery to the machine, it hasheretofore been necessary to subject the pulp to a'beating process forthe purpose of separating the elemental fibers, hydrating, and otherwisetreating them to produce the desired felting or enmeshing on the papermachine. This process is performed in a beating engine and isnecessarily an intermittent or batch process, hereas the paper makingproper is continuous. It is usual to place in the beater a definitequantity of material including unbroken hunks, separated groups of a fewfibers, and some individual fibers ready for the paper machine, and totreat the Whole mass together for a definite period regardless of thefact that a constantly increasing percentage of the mixture becomesready for the paper machine as the treatment progresses.

The action of the beater upon the pulp,

or at least the resultant changes in the pulp Which occur during theheating process, may be generally classed as mechanical and chemical, orphysical and chemical. It is well known, for example, that the fibersare reduced in length and that this physical change takes place largelyduring the early stages of the beating process. As the treatmentprogresses, the fibers are also frayed, split, etc., either in thebeater itself or in the refining engine after the beating proper hasbeen completed. On the other hand, the chemical change, which isprimarily a hydration or a combining of the cellulose fibers With water,takes 'piace more slowly, and is induced by prolonged agitation andfriction rather than by drastic mechanical treatment.

Several different systems tending to make the beating process more orless continuous 1, 1927. Serial No. 216,921.

as applied to' limited classes of paper have been proposed by others.All of these, so far as I am aware, propose to extract particles ofstock from the mass undergoing treatment in the beater. They proceedupon the theory that the fiber or particle is sufficiently treated whenmerely reduced to a certain degree of fineness and without substantialregard to the extent to which the chemical changes in the fiber haveprogressed. Inasmuch as the shortening or reduction in size of the fiberoccurs Ilargely during the early period of the beating, it follows thatfibers continuously extracted from the beater while of the properfineness may be insufficientilir hydrated to form a high grade paper.ence, it is well known, that such systems operate satisfactorily only inthe production of very coarse papers such as roofing felts, leatherboard and the like, and for use in connection with the disintegration ofbroke to half-stuff which is usually circulated in the beater at acomparatively low consistency. Moreover, it has heretofore beenimpossible, from a practical standpoint, to separate or segregateextremely fine particles or fibers from the mass.

My present invention contemplates the substantial hydration of the fiberby agitation or circulation in water prior to any drastic mechanicalaction thereon tending to effect extensive changes in its physicalstructure, and the selection and segre ation of the partially orcompletely hy rated fibers, to be followed, if necessary or desirable,by a mechanical treatment to effect the proper changes in physicalstructure. In other words, instead of producing both the chemical andphysical changes in the fiber simultaneously by a beating process, Ipropose to efiect first, a complete or substantial part of the chemicalchange desired, and thereafter effect such mechanical changes orstructural modifications as may be necessary, depending upon the stockbeing treated and the characteristics sought in the final product. Myinvention also contemplates the continuous selection and segregation ofthe properly hydrated fibers which may or may not, thereafter, besubJeCted to a beating process before delivery to the paper machine.

The primary object of my invention is to provide a more eflicient methodof procedure and means for preparing stock than have been heretoforeknown. Another object is to provide a method and means whereby the stockpreparation process may be carried on substantially any class of paper.

With these objects in view, my invention includes the hereinafterdescribed process,

the apparatus, and the combinations andarrangements thereof which Ibelieve are best' suited to facilitate the performance of my process,and which are described below and illustrated in a more or lessdiagrammatic manner in the accompanying drawings, in

which Fig. 1 is a typical floor plan showing the general layout of amill adapted to use my system;

Fig. 2 is an elevation view, partially in longitudinal section, of Fig.1;

Fig. 3 is a diagrammatic elevation or transverse section of my system,as illustrated in Figs. 1 and 2;

Fig. 4 is. a diagrammatic elevation of a system similar to that shown inFig. 3 and illustrating how beaters may be used in connection with thepreparation of some classes of stock;

Fig. 5 is a longitudinal, vertical section of my hydration or shreddertank in the plane,

. 5-5 of Fig. 6;

Fig. 6 is a horizontal section of Fig. 5 in the plane, 6-6;

Fig. 7 is a transverse section of the shredder or hydration tank in theplane, 77 of Fig. 6;

Fig. 8 is a sectional view of my extractor in a plane normal to theimpeller axis, such as plane, 8 -8, of Fig. 9; and

Fig. 9 is a front elevation of my extractor with a portion of the casingbroken away to show the interior construction to the rear of plane,99,,of Fig. 8.

In preparing stock by my process, the pulp is first shredded into acomparatively large tank, the size of which is somewhat dependentuponmill capacity but which, for example, may be about 100 feet in length,from to feet wide, and about 12 feet deep. The

7 capacity of such a tank at about 4% consistency will be from to tons.The stock is continuously circulated and agitated in this tank, andwhite water and pulp are added continuously or from time to time tomaintain a proper content and a consistency of about 4%.

From this tank, the stock is continuously pumped and offered to suitablestock selectors or extractors which withdraw from the offered stock suchparticles or fibers as have been reduced to the proper size by thehytracted-stock chest but having by-passes therein leading to J ordansor other refining means. The refiners draw continuously from thecirculation system and deliver the re fined stock to the machine chestor mixing pump on the paper machine. For some grades of paper, theextracted stock may be delivered directly to the machine withoutrefining.

Under some circumstances and with some stocks, it may be desirable to soadjust the selectors or extractors that stock particles which have notbeen sufiiciently hydrated or reduced in size by the treatment intheshredder or hydration tank for delivery to the machine proper, will bedelivered to the extracted-stock chest. In this case, the stock may besubjected to a beating process by pumping it from the extracted-stockchest to suitable heaters from which it is dumped in the usual beaterdump chest. From the dump chest, the stock may be delivered to J ordansor other suitable refiners and thence to the machine chest or mixingpump, or, it may be delivered to the machine chest or mixing pumpwithout refining; In any event, the preliminary treatment in-thehydration tank greatly reduces the time required for beating and effectsa great economy in power. It eliminates the uncertainty of insufiicienthydration and resolves the function of the beater into substantially itsmechanica action in changing the physical structure of the fibers.

My process is particularly adapted for the preparation of stock composedof two or more different pulps, such, for example, as

nap

ground wood and sulphite, which are blended together in the finalproduct. Each pulp is separately hydrated and extracted',"and theextracted stocks are delivered to separate. extracted-stock chests..From the chests, the stocks are continuously pumped or otherwisecirculated through separate consistency regulato-rs or metering boxesand the overflow returned to the respective stock chests. From suitablerefiners, and delivered to the mixing pump on the paper machine.

While my process is to be understood as independent of any particularform of apparatus, I have illustrated, in the accomp an y"- ingdrawings, in a more or less typical and diagrammatic manner, the varioussteps therein and the apparatus and the arrangement thereof which Ibelieve best facilitate its performance.

In the drawings, I have illustrated the steps in my process and theapparatus as applied to the preparation of a stock comprising twodifferent pulps, but it is to be understood that the process andapparatus may be used to prepare stock from a single pulp by simplyomitting the steps and apparatus described and illustrated in connectionwith the second pulp.

Referring particularly to Figs. 1, 2 and 3,1 represents a sulphiteshredder drivenby a suitable motor, 2, and adapted to discharge theshredded pulp into the sulphite hydration tank 3." trepresents a groundwood shredder driven by motor, 5, and discharging into the ground woodhydration tank, 6.

The hydration tanks should be comparatively large in capacity, and areprovided with centrally-disposed, longitudinal partitions, 7, similar tothe mid-feather in a heating engine. Near each end of the centralpartition or mid-feather, but on opposite sides thereof, is a transversepartition, 8, ex-

tending from the top to the bottom of the tank and entirely closing thestock passage between the mid-feather and the side of the tank. Thelower portion of each partition,

, on shafts, 11, extending longitudinally of the tanks, provided withsuitable thrust bearings, and having packing glands where they extendthrough the ends of the tanks. The shafts, 11, are driven by motors, 12,acting through suitable gear reductions, 13. White water is supplied tothe tanks through the showers, 1 1, and the consistency of the stock inthe tanks is preferably maintained at about 4%. The tanks are providedwith a slight horizontal slope along the bottom so that they may bedrained and so that stock will flow readily to an outlet pipe, 15, (seeFig. 2) provided in each tank and leading to suitable pumps, 16 and 17driven by motors, 18 and 19, respectively. The pump,

16, circulates the sulphitesto'ck through the sulphite extractors, 20,which accept such particles thereof as are properly hydrated and reducedto the proper size, and delivers them by gravity to the extractedsulphite chest, 21. The particles which are rejected by the extractorsare returned for further treatment to the sulphite hydration tank, 6,through the openings, 22, in the top thereof.

Ground wood from the ground wood hydration tank is circulated throughthe ground wood extractors, 23, by means of the pump, 17 and theaccepted, hydrated particles of proper size are delivered to theextracted ground wood chest, 24:. The particles rejected by the groundwood extractors are returned for further treatment in the hydration tankthrough the openings, 25, in the top thereof.

The preferred type of extractors is substantially identical with thatdescribed in my pending application for pe fent, Serial No. 187,333,filed April 28, 1927, and is illustrated somewhat in detail in Figs.Sand 9 of this application. Referring particular- .ly to these figures,my extractor comprises a casing, 26, having a perforated screen por- 1tion, 27, which is preferably cylindrical, and an impeller, 28, axiallymounted within the casing to revolve with its periphery in close cproximity to the screen. Stock is supplied to the extractors by pumps,16 and 17, respectively, which force the stock through pipes, 32, andspray or project it through a slot, 33, in the side of each pipe andwithin the casing. The stock is preferably projected in a directionabout tangential to the path of the outer edges of the impeller blades 7which are turned at about 400 R. P. M., by

any suitable source of power. The stock particles are swept about theinterior of the casing to the perforated screen, 27, where those whichhave been reduced to the proper size in the hydrating treatment areextruded for delivery to the extracted stock chest. Below the perforatedscreen portion is a trough or gutter, 29, into which fall the particlesof stock extruded through the perforated screen. A screw conveyor, 30,operates in the trough and forces the accumulated particles of stocktoward one end thereof where they are discharged through an opening, 31.Those particles which have not been sulficiently treated are refused bythe extractor and fall back into the hydration tank through openings inthe bottom of the extractor, as indicated by the arrows, 34.

Assuming that only one kind of pulp is being treated, the contents ofthe extractedstock chest may, for some grades of paper. be delivereddirectly to the mixing pump on the paper machine without furthertreatment. For example, the extracted sulphite stock may be withdrawnfrom the chest, 21, by means of pump, 35, (see Fig. 1)- and delivered tothe machine through ipe, 36. In most cases, however, it will be oundadvisable to subject the extracted stock to a refining process bypassing it through one or more J ordans or other refining engines, 37,

before delivery to the machine. In such a a case, the stock iscontinuously circulated from the extracted-stock tank through the ipin38, and back to the tank again (see- 1g. 1 and by-passes, 39, leading tothe refining engines are provided through which the refiners may draw tocapacity. I

Where two separate stocks are being treated which are blended in thefinal product, each stock is continuously circulated through a separatepiping system, such as 38 and 40, by means of pumps, 35 and 41,respectively. By passes, 39 and 42, respectively, are provided in eachsystem leading to separate consistency regulators or metering boxes, 43and 44, respectively. From the consistency regulators, the stocks arelead through a common piping and blended and refined in one or morerefining engines before delivery to the machine. In addition to refiningthe stock, the J ordans efiect the desirable mechanical changes in thepreviously hydrated fibers, and the stock is run through as manyrefiners as may be necessary.

It will be noted that the extracted sulphite chest is provided with anoverflow pipe, 45, leading back to the sulphite hydration tank, and theground wood chest overflows to the ground wood hydration tank throughpipe, 46. Return pipes, 47 and 48, (see Fig. 1) are also provided fromthe machines tothe extracted-stock chests.

Referring particularly to Figs. 1 and 2, it will be understood that theJ ordans, 37, either discharge into other J ordans, as'shown in Fig. 3,and thence to' the machine chest or mixing pump, or discharge directlyto the machine chest or mixing pump through the pipes, 49. Valves,50 and51, in the pipe lines, 40 and 38, respectively, may be provided so thateither the ground wood or sulphite system may be used independently ofeach other in connection with the refining engines; or stock from eithersystem may be delivered direct to the machine by closing these valvesand opening valves, 52 and 53.

Where it is desirable to effect the mechanical changes in the fibers byan actual beating treatment, a considerable economy of time and power iseffected and a better and p more uniform product is obtained by-firsthydrating the stock and delivering it to the' beaters in the form ofparticles which are properly reduced in size and substantially hydrated.i

Fig. 4 illustrates diagrammatically the general arrangement of theapparatus for performing my process in this slightly modified manner,and while it shows the process as applied to two different pulps whichare blended in the final stock, it must be understood as applicable tothe preparation of stock from a single pulp.

The arrangement of the apparatus is substantially the same as describedabove in connection with the process without beaters with the exceptionthat the extracted-stock from each of the stock chests is circulatedthrough separate piping systems, 54 and 55, to separate beaters orbatteries of beaters, 56 and 57 Where ground wood and sulphite pulp arebeing treated for blendin or where any other pulps having natural bersof different lengths or requiring different mechanical treatments arebeing prepared, it is obvious that no greater number of beaters or refinrs will be used than is necessary to effect the desired results. Afterthe stock has been treated in the beaters it may be dumped to a. commondump chest, 58, and delivered from there by means of a pump, 59, to therefining engines, 37', where it is thoroughly blended and refined beforedelivery to the machine. lVhere desirable, the heaters may be dumped toseparate chests, the stocks separately pumped from the dump chests toconsistency regulators, and hereafter passed to the refiners forblending, substantially as described in connection with Figs. 1, 2 and3.

In connection with the general application of my process, it is to beunderstood that variations and modifications in the procedure subsequentto the hydration and extraction steps will be found advisable depending,of course, upon the nature of the stock being treated or prepared andthe kind of paper being made. For example, in some cases the stock maybe delivered to the machine chest or mixing pump with little or nomechanical treatment of the fibers, while in other cases some mechanicaltreatment, such as is obtained by passing the'stock through a J ordanor'other refining engine will be found necessary to obtain the bestresiilts. In still other cases, the stock will require an actual beatingtreatment to effect thedesired changes in the fiber structure. In anyevent, the hydration and segregation of the hydrated fibers prior to anydrastic mechanical action thereon will be found to greatly reduce thetime required in the preparation.

of stock. A great saving in power will be effected, and a markeduniformity of product with less dependence upon the personal equation ofthe operator will result.

It is therefore to be understood that the words which I have usedin'describing my invention are words of description rather than .oflimitation; that the drawings are merely illustrative of the apparatusand arrangements thereof which may be used to perform my process; andthat changes, within the purview of the appended claims may be freelymade without departing from the true scope and spirit of my invention.

What I claim is-- 1. The process of preparing paper' stock from'two ormore'fibrous materials which comprises separately shredding the mate-.rials, separately hydrating by agitation in water without effectingextensive changes in the physical structures of the fibers thereof,segregating from the hydrating materials the fibers, and particles up toa predetermined size, and thereafter blending the segregated portions.

2. The process of preparing paper stock from two or more fibrousmaterials which comprises separately shredding the materials, separatelyhydrating by agitation in water without effecting extensive changes inthe physical structures of the fibers thereof, segregating from thehydrating materials the fibers and particles thereof up to apredetermined size as they become separated from the larger masses, andthereafter subjecting them together to a mechanical treatment forblending and effecting the desired changes in the physical structure ofthe fibers.

3. The process of preparing paper stock from two or more fibrousmaterials which comprises separately shredding the materials, separatelyhydrating by agitation n water without effecting extensive changes 1nthe physical structures of the fibers thereof, segregating from thehydrating materials the fibers and finer particles up to a predeterminedsize as they approach the proper degree of hydration, separately subjectng the segregated portions to a mechanical treatment for producing thedesired changes in the physical structure of the fibers, and thereafterblending the separately prepared fibers.

4. In a pulping system, a device for hydrat ing fibers by agitation andfriction, comprising a tank having a central, longitudinal partitiontherein about which the pulp may be circulated, transverse partitions onopposite sides of the central partition provided with openings thereinnear the bottom of the tank, and screw propellers for forcing acirculation of pulp through the openings in said transverse partitions.

5. In a pulping s stem the combination with a tank adapts to containhydrating pulp, of an extractor comprising a casing with a screentherein adapted to permit the passage of pulp particles of apredetermined size, and'a pump adapted to withdraw pulp from said tankand spray it into the casing of said extractor.

6. In a pulping system, thecombination with a tank adapted to containhydrating pulp, of an extractor and a pump adapted to maintain acirculation of pulp between the tank and extractor and discharge aportion thereof into the extractor.

7. In a pulping system, an extractor comprising a casing, a screenadapted to permit the passage of pulp particles of a predetermined size,an impeller adapted to rotate in said casing in proximity to the screenand a pipe having an opening therein through which pulp may be sprayedinto said casing in a direction substantially tangent to the impeller.

8. In a pulping system, means for hydrating pulp without effectingextensive structural changes in the fibers thereof, means for selectingfrom the hydrating pulp the fibers and particles up to a predeterminedsize as the hydrating pulp between the hydrating and selecting means,and means for beating the selected pulp.

10. In a system for preparing paper stock, a pulp shredder, a hydrationtank adapted to receive the shredded pulp and to contain a comparativelylarge quantity thereof at moderate consistency, means for maintaining acirculation of pulp in said tank, means for selecting and segregatingfibers and particles of pulp up to a predetermined size, means formaintaining a circulation of pulp between the tank and the selectingmeans, a Jordan, and means for maintaining a continuous flow 3f pulpfrom the selecting means to the J or- 11. In a system for preparingpaper stock from two or more fibrous materials,- separate shredders foreach material, separate hydration tanks adapted to receive the shreddedpulp, separate extractors adapted to select and segregate fibers andparticles of pulp up to a predetermined size, means for maintaining acirculation of pulp between each tank and an extractor, means forcontinuously intermixing the separately extracted pulps,

means for regulating the consistency of each pulp before intermixing,and means for blending and refining the intermixed pulps. 12. In asystem for the continuous preparation of paper stock, a hydration tankadapt ed to contain a substantial quantity of shredded pulp at moderateconsistenc means -for selecting and segregating pulp fi ers andparticles of pulp up to a predetermined size, means for maintaining acontinuous circulation of pulp through thetank and the selecting means,means for regulating the consistency of the selected pulp and means formaintaining a continuous flow of, selected pulp to the regulating means.

13. In a system for the continuous prepara- A tion of paper stock, atank adapted to contain a substantial quantity of shredded pulp atmoderate consistency, means for selecting and segregating pulp fibersand particles of pulp up to a predetermined size, means for maintaininga continuous circulation of pulp.

through the tank and the selecting means, a main pipe line, means formaintaining a continuous circulation of selected pulp in said line, andby-passes from said line adapted to size, means for maintaining acontinuous circulation of pulp through each tank and its associatedselecting means, a separate main pipe line for each pulp, means formaintaining a continuous circulation of selected pulp in each line,by-passes from each line adapted to convey continuous supplies of pulpto separate consistency regulators, and means for continuously blendingthe pulps flowing from the regulators.

15. In apulping system, a device for disintegrating and hydrating pulpwithout efiecting extensive structural changes in the fibers thereofcomprising a tank approximating a beater tub in shape, a mid-feathertherein providing a continuous horizontal passage for the circulation ofpul transverse partitions on opposite sides of t e mid-feather proscrewvided with openings therein normally submerged, and screw propellersrotatively mounted in said openin for forcing a circulation of pulp inthe tanfi.

16. In a system for. preparin paper stock, the combination with a tank aapted to contain a substantial volume of water and raw stock to bedisintegrated, ,of a plurality of propellers rotatably mounted thereinfor agitating the contents of said tank to efi'ect a breaking up andhydration of the raw material, and means forseparating thefibers andfiner particles of stock from the general mass as the disintegrationprogresses.

'17. That order of steps in the preparation of paper stock whichcomprises, hydrating pulp by comparatively rapid circulation in waterbut without drastic mechanical treatment tending to break or effectchanges in the physical structure of the individual fibers,simultaneously -segregating from the hydrating pulp the fibers andsmaller particles thereof, and then effecting the neces sary changes inthe physical structure of the segregated fibers by subjecting them tomechanical treatment.

18. In a system for the preparation of paper stock, the combination'witha tank of .comparatively, large-volume provided with screw propellersro'tatively mounted therein, for disintegrating and hydrating pulp byrapid circulation in water without producing substantial changes in thephysical structyre of the individual fibers thereof, of means fordriving said propellers, means for subsequently effecting the desiredchanges in physical fiber structure by mechanical action thereon, andmeans for maintaining a continuous flow of pulp from the hydrating tankto the structure changing means.

19. In a system for preparing paper stock, thecombination with means forresolving the material substantially into its elemental fibers andhydrating to a substantial degree without extensively aflecting thephysical structure of the fibers and comprisin a tank of comparativelylarge volume provi ed with screw propellers, rotatably mounted therein,of means for separating and segregating, as the hydrating treatmentprogresses, the fibers and smaller particles of stock, means forefiectin the desired changes in physical structure -0 the segregatedfibers, and means for maintaining a continuous now of material from thehydrating means'through the segregating means to the structure changingmeans.

20. In a pulping system adapted to prepare paper stock from two or morefibrous materials, the combination with separate tanks of large volumeprovided with screw propellers rotatively mounted therein fordisintegrating the materials and effecting the desired chemical changestherein to a substantial degree without extensively affecting thephysical structure of the fibers, of separate means for continuouslywithdrawing and segregating the fibers and finer particles of eachmaterial from the disintegratin tanks, means for blending the segregatedportions together in the desired proportion, means for efl'ecting thedesired structural changes in the fibers of the blended stock, and meansfor maintaining a flow of the segregated material through the blendingmeans to the structure changing means.

' 21. In a pulping system, a device for disintegrating and hydratingpulp without effectmg extensive structural changes in the fibersthereof, such as take place in a beater,

comprising a tank of comparatively large volume having, a continuous.horizontal passage therein for the circulation of pulp a partitionacross said passage provided w1th a normally submerged opening thereinof much smaller area than the normal cross sectional area of saidpassage, a screw propeller rotatively mounted in said opening forforcing a circulation of pulp in said passage, and means for drivingsaid propeller to effeet a rapid circulation of the pulp.

22. In a pulping system, a device for-disintegrating and hydrating pulpwithout effecting extensive structural changes in the" fibers thereof,such as take place in a heater, comprising a tank of comparatively large"ing said propeller to force a rapid circulation of pulp through saidopening.

23. In a pulping system, a device for dis-' integrating and hydratingpulp without effccting extensive structural changes in the fibersthereof, such as take place in a beater, comprising a tank having acontinuous horizontal passageway therein of relatively large crosssectional area and volume for the circulation of pulp, but having spacedcross sections thereof of restricted area, screw propellers rotativelymounted in said cross sections of restricted area, and means for drivingsaid propellers to, force a rapid circulation of pulp through thepassageway;

24. Ina pulping system, a device for disintegrating and hydrating pulpwithout effecting substantial structural changes in the fibers thereof,such as occur in beating, com--.

prising a tank having a continuous horizontal passageway therein ofrelatively large cross section and volume for the circulation of pulpbut having spaced cross sections thereof provided with a plurality ofpassageways of restricted area near the bottom of the tank, screwpropellers rotatively mounted in said restricted passageways, and meansfor driving said propellers to force a rapid circulation of pulp throughthe tank.

25. In a pulping system, the combination with a tank, of a fiberextractor, a screw propeller for circulating the pulp through said tankto effect a hydration thereof, and independent means for maintaining acirculation of the hydrating pulp through the tank and extractor.

26. In a pulping system, a tank, screw propellers in said tank forforcing a rapid circulation of pulp therein without drastic mechanicalaction, such as takes place in a beater, means for selecting from thehydrating pulp the smaller particles and fibers thereof as they approachthe desired degree of hydration, means for maintaining a circulation ofpulp between said tank and the selecting means, means for refining theselected pulp, and means for maintaining a flow of selected pulp to therefining means.

27. A device for disintegrating and bydrating raw material for thepreparation of paper stock comprising a tank adapted to contain asubstantial volume 'of water and material, a plurality of screwpropellers rotatably mounted therein for agitating the contents of saidtank, a screen, and means for creating a flow of fibers and smallerparticles of stock through said screen as the disintegration progresses.

28. A device for disintegrating and hydrating material for thepreparation of paper stockcomprising a vat-like tank adapted to containlarge tonnages of water and material to be treated, a plurality of screwpropellers mounted in the lower portion thereof to rotate in verticalplanes entirely submerged, means for driving said propellers at a speedadapted to create a substantial agitation of the tank contents and toefiect a breaking up of masses of material therein, and means ex tendingover said propellers for restraining upthrow of material therefrom andcooperating therewith to produce a rapid circulation of stock.

GEORGE STANFORD WITHAM, JR.

